1. Field of the Invention
The present invention generally relates to printing patterns on photosensitive surfaces.
2. Related Art
A printed pattern in a generic, maskless lithography tool is formed from a sequence of exposures, or shots. Each shot results from an image of a spatial light modulator (SLM) array being projected onto the surface of a photosensitive surface, such as a wafer substrate. This results in deposition of a dose, or a quantity of irradiation from a light source, within a certain exposure zone on this surface. Exposure zones are created when the substrate surface is illuminated by flashes of light from the light source. When the pattern extends beyond the boundaries of exposures of a single SLM, the exposures are stitched together along adjacent boundaries to form a completed pattern.
Stitching errors in the printed pattern occur near these boundaries between adjacent exposure zones due to both geometrical misalignments of the exposures and disturbances due to other optical phenomena. Generally, stitching errors occur in printed patterns due to spatial misalignment of the exposure zone on the wafer from its expected position. Optical effects may also create stitching errors, even in cases where the alignment may be perfect. Even a small spatial misaligmment of the shots, in the case of a spatial misalignment, may result in a significant perturbation of the printed pattern near the stitching line.
The optical effects are due to the fact that distribution of the dose within each exposure zone is a result of an exposure by partially coherent light. Since two adjacent exposure zones are exposed at different times, the exposures are effectively incoherent, thus creating the unwanted optical effects.
Therefore, what is needed is a solution to compensate for stitching errors in printed patterns that occur near the stitching line between adjacent exposure zones.